"Bill Pragnell" <bil### [at] hotmailcom> wrote:
> "Bruno Cabasson" <bru### [at] alcatelaleniaspacefr> wrote:
> > I recently worked on the question of clouds
> Hi Bruno!
>
> I have to say, these are awesome clouds. If I can get my cumulus looking
> half as good as this... :) Most of these images appear to have clouds as
> continuous layers - are these isosurface clouds? And I notice there are
> some 'fringing' glows when the sun is behind the clouds - does this
> behaviour occur naturally when you move the light source or does it require
> different media?
>

No they are scattering media between two planes (for one layer). I use
built-in patterns (bozo, crackle, wrinkles, spiral, ...) Scattering type is
2 (MIE_HAZY_SCATTERING), which corresponds to natural clouds and to what is
said in the documentation about scattering (3.6.2.1.3  Scattering). This
produces the effect whith the sun. But I can chose the scattering tpe

Until now, I can define 3 independent layers, and 5 individual clouds, plus
a specific layer for some kind of oveall mist (plus fog of course, plus
another specific dispersive layer ...). It seems to be enough for most
cases. But I am still in trial phase, improving and trying to find an
easy-to-use way to make acceptable clouscapes. I got inspired by Terragen.

One of the problems was to contol the turbulence parameters. And my model is
not really suitable for large fat and round cumuli that have a flat base,
round turbulences, and can go high in the verical dimension. Though my
individual clouds do have a flat base and might look like cumuli. But
observing nature makes me see I and lightyears from it.

> > and I found that one should
> > separate cloud layers from individual clouds.
> I'm not sure I understand what you mean by this... do you mean to use either
> one or the other?

I ment that I never could make good cloudscapes with individual clouds. And
I frequently encounter problems with the containers when they overlap,
mostly if the whole scene is also surrounded by media.
>
> > But I would not recomment adjusting the
> > aspect via emission. First because it does not correspod to reality, and
> > second because it will interact with radiosity in a wrong manner.
> Yes, I'd rather not have used emission, but it did make a big difference. As
> to reality - well, the effect I'm looking for would have to be simulated by
> media interacting with itself via radiosity, which I don't believe is
> possible.
>
> > Btw: can I attach more than one image in a post?
> Not via the web interface. With a newsreader, I believe so.
>
> > Now I am working on some other features: sun aspect (halo ...)
> I'd like to see that when you have some results!
>
> Bill

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